The present invention relates to a merchandise checkout system in which an electronic cash register or terminal device is used in conjunction with a credit card reader to increase the speed of the checkout operation. The use of credit cards, either in the form of small plastic cards, plates or the like has become so widespread in merchandise transactions that the checking of credit authorization through use of the credit card is a standard part of today's merchandising checkout operation. Most prior art credit card systems store credit information at a central data station. In response to the submission of an account number from a remote credit reader, the system provides information relating to the account. For instance, the system may indicate that the credit card has been stolen, has expired, whether the account has been overdrawn or may indicate the dollar amount of available credit. One system magnetically imprints a dollar amount on the credit card that may be spent during a predetermined length of time. After a sales transaction is completed, the system subtracts the amount of the transaction from the available balance and rewrites the new balance on the card. Other systems will simply store the new balance at the central station. Common to all of these prior checkout systems which include a terminal device and a credit card reader is the requirement for the operator to operate the credit card reader after totalling the merchandise to check if the customer is authorized to use the credit card in paying for the merchandise purchased. This requires the customer to give the credit card to the operator with the operator then inserting the card in the card reader orientated in a predetermined position to provide a valid read operation. Such requirement measurably increases the time of the checkout operation in addition to complicating the checkout routine of the operator, the latter tending to increase operator errors during the checking of the merchandise at peak hours. Prior art arrangements have also been directed to systems for identifying the owner of the card or to provide a visible indication that the credit card is valid and may be used in paying for the merchandise purchased. In all cases, the operator is again required to perform the card reading operation. It is therefore a primary object of this invention to provide a merchandise checkout system capable of executing a checkout operation which includes a credit authorization procedure in the minimum amount of time. It is a further object of this invention to provide a checkout system which includes a terminal device and credit card reader, both of which are operated simultaneously by the checkout operator and the customer respectfully. It is another object of this invention to provide a checkout system in which the amount read from the credit card is entered into the data terminal and used to prepare the customer's receipt showing the amount paid and, in case of a credit balance less than the total of the merchandise amount, the money amount due from the customer to complete the sales transaction.